Evaporator For Loop Heat Pipe System

ABSTRACT

Provided is an evaporator for a loop heat pipe system including a condenser, a vapor transport line, and a liquid transport line, and more particularly, to an evaporator having an increased contact area between a sintered wick and a heating plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of pending Internationalpatent application PCT/KR2008/004493 filed on Aug. 1, 2008 whichdesignates the United States and claims priority from Korean patentapplication 10-2008-0057458 filed on Jun. 18, 2008, the content of whichis incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an evaporator for a loop heat pipesystem including a condenser, a vapor transport line, and a liquidtransport line, and more particularly, to an evaporator having anincreased contact area between a sintered wick and a heating plate.

BACKGROUND OF THE INVENTION

Electronic parts such as CPUs or semiconductor chips used for variouselectronic devices such as computers generate a large amount of heatduring operation. Such electronic devices are usually designed tooperate at room temperature. Accordingly, when heat generated during theoperation of an electronic device is not effectively cooled down, theperformance of the electronic device is severely deteriorated and, insome cases, the electronic device itself may be damaged.

In order to cool down heat generated by various electronic parts, manyapproaches have been developed, such as a heat conduction method using aheat sink, a method of using natural convection or radiation of air, aforce convection method using a fan, a method using circulation ofliquid, or a submerged cooling method.

However, as nowadays many electronic products are made slim, aninstallation distance between electronic parts generating heat duringoperation is continuously decreased so that heat is not appropriatelycooled down. Also, since the heat load of electronic parts hascontinuously increased due to the high integration and high performanceof the electronic parts, the above-described cooling methods are notable to effectively cool down the electronic parts.

As a new technology to solve the above problem, a phase change heattransport system which can cool down an electronic part having a highheat load density per unit has been introduced. A thermosyphon systemand a cylindrical heat pipe system are examples of the phase change heattransport system.

According to the thermosyphon system, cooling is achieved using anatural circulation method via a liquid-vapor phase change and aspecific gravity difference of working fluid. In a conventionalcylindrical heat pipe 100, as shown in FIG. 1, cooling is obtained bycirculating the working fluid using a capillary pumping force generatedby a sintered wick installed in an inner surface of a pipe. When heat istransported from a heat source 101, the working fluid included in thesintered wick 102 is evaporated and moved in a direction indicated by aplurality of arrows 103 as a flow of vapor. As the heat is dissipated bya heat sink 104, the operating fluid is changed back to a liquid stateand moved along the sintered wick 102 in a direction indicated by aplurality of arrows 105, thereby circulating in the heat pipe 100.

However, there is a limitation in the positions of the constituentelements of the two systems, that is, the thermosyphon system requires acondensing portion located higher than an evaporating portion and,although this problem is less severe in the case of the heat pipe 100, aheat transport ability of the heat pipe 100 is quite deteriorated when acondensing portion is located lower than the evaporating portion.Accordingly, this limitation prevents electronic devices employing theabove cooling systems from being made slim.

Also, since vapor and liquid flow in opposite directions in a linearpipe of the thermosyphon or the cylindrical heat pipe 100, the vapor andthe liquid may be mixed in the middle of the pipe. Another problem isthat the mixture may make the amount of heat actually transported lessthan that that can be ideally transported.

A loop heat pipe (LHP) system has been suggested as an ideal heattransport system which can solve these problems, that is, the positionallimitation and the mixture between the vapor and liquid. The LHP systemis a sort of a capillary pumped loop heat pipe (CLP) technologydeveloped by the NASA, U.S.A., to cool down a large amount of heatgenerated from communications equipment or electronic equipment for anartificial satellite.

Korean Patent No. 671041 entitled “Loop Heat Pipe” discloses atechnology about a compact loop heat pipe system. FIG. 2 illustrates aloop heat pipe system 110 according to this conventional technology. Theconventional loop heat pipe system 110 includes a condenser 112, anevaporator 114, and a vapor line 116 and a liquid line 118, which form aloop. The vapor line 116 and the liquid line 118 are connected betweenthe condenser 112 and the evaporator 114. In the loop heat pipe system110, a sintered wick 120 is installed only in the evaporator 114 unlikethe conventional linear heat pipe of FIG. 1.

In the present specification, the loop heat pipe is referred to as aloop heat pipe system and both terms have the same meaning. Also, theevaporator and the condenser, respectively, have the same meanings asthe evaporator section and the condenser section.

The loop heat pipe system 110 operates in the following manner. Heat isapplied to a heating plate 122 which is the bottom portion of theevaporator 114 which is inserted with the sintered wick 120. At thatpoint the sintered wick 120 is saturated with the liquid phase ofworking fluid due because the heat transported to the sintered wick 120contacting the heat plate 122. And the applied heat vaporizes theworking fluid so that the phase of the working fluid is changed to avapor state. The vapor is moved toward the condenser 112 along the vaporline 116 connected to a side of the evaporator 114. As the vapor passesthrough the condenser 112, heat is dissipated externally so that thevapor is liquefied. The liquefied working fluid is moved toward theevaporator 114 along the liquid line 118 at a side of the condenser 112.The above-described process is repeated so that the heat source can becooled down.

In the evaporation of the working fluid permeated in the sintered wick120, referring to FIG. 4 showing the sintered wick 120 of FIG. 3 rotatedby 180° for the convenience of explanation, a surface 126 of thesintered wick 120 facing the heating plate 122 includes a contactsurface 126 b contacting the heating plate 122 and a plurality ofmicro-channels 126 a working as a passage of the generated vapor.Accordingly, the sintered wick 120 receives heat via the contact surface126 b contacting the heating plate 120 so that the received heat makesthe operating fluid permeated in the sintered wick 120 evaporate. Thegenerated vapor is moved toward the condenser 112 along the vapor line116 connected to a side of the evaporator section 114 through themicro-channels 126 a formed in the surface 126 facing the sintered wick120.

On the other hand, the performance of an evaporator taking heat from aheat source like an electronic part is determined according to how wellthe heat transported from the heat source to a heating plate istransported to a sintered wick. In this connection, contact conductanceis a factor directly affecting the heat transport between the heatsource and the heating plate.

The contact conductance is related to the thermal resistance generatedwhen a metal has a surface contact with another metal and heat transportoccurs between the metals. The contact conductance is proportional tothe contact area between the two metals. That is, as the contact areaincreases, the contact conductance increases, and as the contactconductance increases, heat transport is generated further.

However, in the evaporator for the conventional loop heat pipe system,since the contact area between the sintered wick and the heating plateis decreased due to the existence of a vapor passage, that is, themicro-channels, the contact conductance is relatively small. That is,referring to FIG. 5 showing the sintered wick 120 having themicro-channels 126 a coupled to the heating plate 122 in a directionrotated by 90° from the direction of the cross-section of FIG. 3, thecontact surface 126 b of the sintered wick 120 contacting the heatingplate 122 is decreased due to the micro-channels 126 a so that theamount of heat to be transported is reduced accordingly.

SUMMARY OF THE INVENTION

The present invention provides an evaporator for a loop heat pipesystem, the evaporator having increased contact conductance byincreasing a contact area between a metal sintered wick and a heatingplate.

According to an aspect of the present invention, there is provided aAccording to an aspect of the present invention, there is provided anevaporator for a loop heat pipe system includes an evaporator sectionhaving a sintered wick formed by sintering a metal powder, in which aworking fluid permeating through a plurality of pores in the sinteredwick is heated so that the phase of the working fluid is changed to avapor state, a condenser section in which the phase of the working fluidtransported from the evaporator section is changed from a vapor state toa liquid state, a vapor transport line connecting between the evaporatorsection and the condenser section to transport the working fluid, whosephase is changed to a vapor state by the evaporator section, to thecondenser section, and a liquid transport line connecting between thecondenser section and the evaporator section to transport the workingfluid, whose phase is changed to a liquid state by the condensersection, to the evaporator section, wherein the evaporator sectionincludes a heating plate formed of metal and receiving heat from a heatsource, a sintered wick coupled to a surface of the heating plate andreceiving heat, a plurality of grooves formed in a surface of theheating plate contacting the sintered wick and functioning as a passagethough which the working fluid whose phase is changed to a vapor stateby the sintered wick is exhausted through the vapor transport line,wherein the grooves are formed in a side surface of the heating plate,each of the grooves having a bottom surface and two side surfaces, andthe sintered wick is partially inserted in each of the grooves so as tocontact at least a part of the two side surfaces of each of the grooves.

The part of the sintered wick inserted in each of the grooves may be aninsertion portion, both side surfaces of the insertion portion contactthe two side surfaces of each of the grooves, and a lower surface of theinsertion portion is any one of a downwardly bulging shape, an inwardlydepressed shape, and a flat shape.

The heating plate may include a lower plate portion having a circulardisc shape and a wall portion extending from a circumferential portionof the lower plate portion, the sintered wick may be coupled to an innersurface having an upper surface of the lower plate portion and an innersurface of the wall portion of the heating plate, and a cover member isprovided in an upper portion of the wall portion of the heating plateand the liquid transportation line is coupled to the cover member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the operation of a conventional cylindrical heatpipe;

FIG. 2 illustrates the concept of a conventional loop heat pipe;

FIG. 3 is a cross-sectional view of a conventional evaporator of FIG. 2;

FIG. 4 is a perspective view of the sintered wick of FIG. 3 rotated by180°;

FIG. 5 is a cross-sectional view of a portion of the sintered wick andthe heating plate of the conventional evaporator of FIG. 2;

FIG. 6 is a perspective view of a loop heat pipe system including anevaporator according to an embodiment of the present invention;

FIG. 7 is a cross-sectional view of the evaporator of FIG. 6;

FIGS. 8, 9, and 10 are cross-sectional views of the sintered wicks ofFIG. 7 according to embodiments of the present invention;

FIG. 11 is a cross-sectional view illustrating a state in which thesintered wick and the heating plate are coupled to each other; and

FIG. 12 is a perspective view of the heating plate where a groove isformed.

DETAILED DESCRIPTION OF THE INVENTION

The attached drawings for illustrating exemplary embodiments of thepresent invention are referred to in order to gain a sufficientunderstanding of the present invention, the merits thereof, and theobjectives accomplished by the implementation of the present invention.Hereinafter, the present invention will be described in detail byexplaining exemplary embodiments of the invention with reference to theattached drawings. Like reference numerals in the drawings denote likeelements.

The present invention is related to an evaporator for a loop heat pipesystem including a condenser, a vapor transportation line, and a liquidtransportation line. FIG. 6 illustrates the structure of a loop heatpipe system according to an embodiment of the present invention.Referring to FIG. 6, the loop heat pipe system includes an evaporator 1,a condenser 210, a vapor transport line 220, and a liquid transport line230.

The condenser 210 changes the phase of a working fluid in a vapor statereceived from the evaporator 1 to a liquid state. The condenser 210takes heat from the working fluid and exhausts the heat to the outsideair.

The vapor transport line 220 is a pipe member connecting the evaporator1 and the condenser 210 to supply the vapor whose phase is changed bythe evaporator 1 back to the condenser 210. The liquid transport line230 is a pipe member connecting the condenser 210 and the evaporator 1to supply the liquid whose phase is changed by the condenser 210 back tothe evaporator 1.

The general operations of the condenser 210, the vapor transport line220, and the liquid transport line 230 are the same as those describedin the background section. The evaporator 1, which is the subject matterof the present invention, is one of the constituent elements of the loopheat pipe system, together with the condenser 210, the liquid transportline 220, and the vapor transport line 230.

FIG. 7 is a cross-sectional view of the evaporator 1 of FIG. 6.Referring to FIG. 7, the evaporator 1 includes a sintered wick 20 thatis formed by sintering metal powders. When the working fluid permeatingthrough pores formed inside the sintered wick 20 is heated, the phase ofthe working fluid is changed to a vapor state. The evaporator 1 includesa heating plate 10, the sintered wick 20, and a plurality of grooves 30.The heating plate 10 is formed of metal and receives heat from a heatsource such as electronic parts that generate heat during operation.

In the present embodiment, the heating plate 10 includes a lower plateportion 12 and a side wall portion 14. The lower plate portion 12 has adisc shape. The side wall portion 14 extends upwardly from thecircumferential portion of the lower plate portion 12. The lower plateportion 12 and the side wall portion 14 may be integrally formed orcoupled together after being manufactured separately. The lower surfaceof the lower plate portion 12 contacts the heat source and receives heatfrom the heat source. The heat transported to the lower plate portion 12is transported to the side wall portion 14 connected to the lower plateportion 12 by conduction.

In the present embodiment, a cover member 16 is provided at an upper endportion of the side wall portion 14 of the heating plate 10. The liquidtransport line 230 is connected to the cover member 16 so that theworking fluid in a liquid state transported from the condenser 210 flowsinto an inner space of the evaporator 1. An inlet 17 to which the liquidtransport line 230 is connected is formed in the cover member 16 of theevaporator 1 so that the working fluid can flow into the evaporator 1.An outlet 18 to which the vapor transport line 220 is connected isformed in the heating plate 10 so that a vapor can be exhausted.

In the present embodiment, the lower plate portion 12 of the heatingplate 10 has a disc shape and the side wall portion 14 has a shapeencompassing the lower plate portion 12. The cover member 16 has a discshape and is provided on top of the heating plate 10. The evaporator 1has a hollow cylindrical shape. However, the present invention is notlimited to the above descriptions and, for example, the lower plateportion may have a polygonal plate shape such as a rectangle.

The sintered wick 20 is coupled to the upper surface of the lower plateportion 12 to receive heat therefrom. The working fluid in a liquidstate included in the pores of the sintered wick 20 is evaporated into avapor state by the received heat. The sintered wick 20 is formed bysintering a metal powder. A large number of spaces or pores are formedin the sintered wick 20 so that the working fluid in the liquid statecan permeate in the sintered wick 20. The groves 30 are formed in asurface where the heating plate 10 and the sintered wick 20 contact eachother and work as a passage for a vapor in the sintered wick 20 whosephase is changed to exhaust vapor through the vapor transport line 220via the outlet 18. Thus, since the groves 30 are connected to the outlet18, the vapor can be exhausted from the evaporator 1 through the vaportransport line 220.

In the present embodiment, the grooves 30 linearly formed in the uppersurface of the lower plate portion 12 are separated from one another andparallel to one another. Each space (not shown) is circumferentiallyformed at both end portions of each of the grooves 30. Also, the grooves30 are circumferentially formed in the side wall portion 14. Each spacepenetrating the grooves 30 and connected to the outlet 18 is formed inthe side wall portion 14. Accordingly, the vapor generated in thegrooves 30 formed in the lower plate portion 12 of the heating plate 10flows toward the space formed in the circumferential portion of thelower plate portion 12 and then is exhausted via the outlet 18 towardthe vapor transport line 220. Also, the vapor generated in the grooves30 formed in the side wall portion 14 of the heating plate 10 flowstoward the space penetrating the grooves 30 and the resultant vapor thentravels via the outlet 18 toward the vapor transport line 220.

Each of the grooves 30 has a bottom surface 32 and side surfaces 34 andis formed on a side surface of the heating plate 10. In the presentembodiment, the term “a surface” of the heating plate 10 has the samemeaning as an “inner side surface” and indicates the upper surface ofthe lower plate portion 12 and an inner surface of the side wall portion14. Accordingly, the grooves 30 are formed in the inner side surface, orthe side surface, that is, in the upper surface of the lower plateportion 12 and the inner surface of the side wall portion 14 of theheating plate 10.

The sintered wick 20 is coupled to the inner side surface of the heatingplate 10 to receive heat. In particular, the sintered wick 20 ispartially inserted into each of the grooves 30 so as to contact at leastpart of both side surfaces 24 of each of the grooves 30. In the presentembodiment, the part of the sintered wick 20 inserted in each of thegrooves 30 is referred to as an insertion portion 22.

Both side surfaces 24 of the insertion portion 22 contact the upperportions of the side surfaces 34 of the grooves 30. The insertionportion 22 is inserted in each of the grooves 30 to a depth of about ⅓of the height of each of the grooves 30. A lower surface 26 of theinsertion portion 22 has a flat shape. An insertion length t of aportion of the insertion portion 22 inserted into each of the grooves 30is defined as a length of both side surfaces of the insertion portion 22coupled to both side surfaces of each of the grooves 30 assuming thatboth side surfaces of the insertion portion 22 are symmetrical.

However, the insertion length t of the insertion portion 22 and theshape of the lower surface 26 may be interdependently changedconsidering factors such as a contact area between the heating plate 10and the sintered wick 20, a need for the space in the grooves 30 as thepassage of the vapor, the size of a surface area where the working fluidcan be evaporated. That is, the length t of the insertion portion 22 maybe determined as a predetermined value considering the above factors.

For example, referring to FIG. 8, a lower surface 26 a of an insertionportion 22 a downwardly bulges in interrelation with a change in theinsertion length t. Referring to FIG. 8, a lower surface 26 b of aninsertion portion 22 b is inwardly depressed. Also, referring to FIG.10, the insertion length t of an insertion portion 22 c of the sinteredwick 20 with respect to the side surfaces 34 of the grooves 30 is almostequal to the height of each of the grooves 30 and a lower surface 26 cof the insertion portion 22 c is inwardly depressed. The shape of thelower surface 26 c of the insertion portion 22 c can maximize thecontact area between both side surfaces 24 of the sintered wick 20 andboth side surfaces 34 of the grooves 30 of the heating plate 10 andsimultaneously enables the grooves 30 to work as a vapor passage, andalso facilitates securing a sufficient area of the lower surface 26 c.

In the evaporator for a heat pipe system of the present embodiment,since the insertion portion 22 of the sintered wick 20 is inserted ineach of the grooves 30 formed in the heating plate 10 and contacts bothside surfaces of each of the grooves 30, the contact area increases. Theincrease in the contact area is described with reference to FIGS. 11 and12.

FIG. 11 is a cross-sectional view illustrating a state in which asintered wick 20 d and the heating plate 10 are coupled to each other.FIG. 12 is a perspective view of the heating plate 10 where a pluralityof grooves 30 d are formed. In FIGS. 11 and 12, it is assumed that thesintered wick 20 d and the heating plate 10 are not circular butrectangular for the convenience of calculation, an n-number of grooves,where n is an integer, each having the same length, are formed in theheating plate 10, and the lower surface of an insertion portion is flat.Accordingly, since the shapes of the sintered wick 20 d and the grooves30 d are different from those shown in FIG. 7, a suffix “d” is added toreference numbers for the sintered wick 20 d and the grooves 30 d.

In FIGS. 11 and 12, the meanings of reference characters are as shownbelow.

W′: heating width W: width of groove H: height of groove L: length ofgroove n: number of grooves r_(tw): permeation ratio of insertionportion A′: contact area r_(w): insertion length ratio A: vaporevaporation A_(tw): permeation area A_(t): total area area

W′×L=A′, W×L=A, A_(t)=n(A′+A)

When the ratio of the heating area to the total area is that r_(w)=W/W′,nA′/A_(t)=nW′L/n(W′L+WL)=W′/(W′/W)=1/(1+r_(w)). If the sintered wick 20d is inserted into each of the grooves 30 d by a depth of t and bothside surfaces of an insertion portion are symmetrical, the amount of anincrease in the contact area is as follows.

When r_(tw)=2t/W, A_(tw)=2tL=r_(tw)WL. Accordingly, the contact area isthat A′=n(W′L)+n(r_(tw)WL)=nL(W′+r_(tw)W). Thus, the ratio of a heatingarea increased as the sintered wick 20 d intrudes into each of thegrooves 30 d is thatnA′/A_(t)=nL(W′+r_(tw)W)/nL(W′+W)=(W′+r_(tw)W)/(W′+W)=(1+r_(tw)r_(w))/(1+r_(w)).

Generally, the size and number of the grooves 30 d are determinedaccording to the specification of a system. Since the increase in thecontact area decreases the value of heat flux (W/m²), it is preferablethat the contact area is increased. When the contact length ratio r_(w)is 0.5, as the permeation ratio r_(tw) increases to 0.1-0.5, the contactarea ratio is increased to 0.7-0.83. Compared to a case when thepermeation ratio is 0, the contact area ratio is increased to 0.7-0.83from 0.67 by 0.03-0.17. Accordingly, when the permeation ratio r_(w) is1, that is, t=W/2, or more, the contact area may correspond to an areaof insertion may be larger.

A method of coupling the sinters wick 20 to a side surface of theheating plate 10 may be a sintering method of sintering metal powder toform the sintered wick 20 and simultaneously coupling the sintered wick20 to the heating plate 10 and a coupling method of forming the sinteredwick 20 and then coupling the sintered wick 20 to the heating plate 10where the grooves 30 are formed. The coupling method includes a simplepressing coupling method and a metal coupling method.

According to the simultaneous sintering method, a plurality of groovesare formed in a metal heating plate and the grooves are filled with asublimate solid material considering the insertion length of aninsertion portion and the shape of a lower surface of a sintered wick.That is, in FIG. 7-9, a portion of each of the grooves, corresponding toan empty space, is filled with the sublimate solid material consideringthe insertion portion inserted in each of the groves. Then, a jig abovethe sintered plate is arranged to be separated from one another by thethickness of the sintered wick. The heating plate and the jig are packedwith metal powder and heated at a predetermined temperature for a periodof time according to the type of the metal powder to be sintered. As themetal powder is sintered, the metal powder is coupled to the heatingplate. Also, simultaneously with the sintering of the metal powder, thesublimate solid material filling the grooves is sublimated and exhaustedfrom the sublimate solid material. Accordingly, with an empty spacehaving a desired shape, the insertion portion of the sintered wickinserted in each of the grooves is formed into a desired shape.

In the simple pressing coupling method, a previously manufactured metalsintered wick is prepared to contact the heating plate and then apredetermined load is applied to the sintered wick to be coupled to theheating plate. In the metal coupling method, a previously manufacturedmetal sintered wick is prepared to contact the heating plate and heatedto be sintered again (or secondly sintering) so that the sintered wickis coupled to the heating plate. Any one of the above-described methodsmay be appropriately selected as a method of coupling the sintered wick20 to the side surface of the heating plate 10.

As described above, according to the evaporator for a loop heat pipesystem according to the present invention, since the contact areabetween the heating plate and the sintered wick is increased compared tothe conventional technology, a contact conductance increases. That is,in the conventional technology, the heating plate and the sintered wickcontact each other except for a surface corresponding to the width ofeach of the grooves functioning as a passage for vapor. In theevaporator of the present invention, since a portion of the sinteredwick is inserted in each of the grooves and contacts both side surfacesof each groove, the contact area between the heating plate and thesintered wick increases.

Also, according to the evaporator for a loop heat pipe system of thepresent invention, since the shape of the lower surface of the insertionportion of the sintered wick inserted in each of the grooves can bevariously formed, in a state in which the contact area between theheating plate and the sintered wick is increased, a sectional area ofthe vapor passage and a evaporation surface area can be additionallyadjusted so that optimal efficiency suitable for the environment can beobtained.

Furthermore, according to the simultaneous sintering method, since amanufacturing process is simple, a cost for manufacturing an evaporatoris low. In particular, since the coupling between the sintered wick andthe heating plate is performed simultaneously with sintering, a contactstate is improved so that contact conductance is increased. Also, bycontrolling a state of a sublimate material filling the grooves, theinsertion portion of the sintered wick can be formed in any shape.

In addition, when the sintered wick is coupled to the heating plate inthe coupling method, compared to the above-described simultaneoussintering method, the coupling state between the sintered wick and themetal heating plate is slightly deteriorated. However, since the sidesurface of the insertion portion is coupled to the side surface of eachof the grooves, compared to the conventional technology, the contactarea between the sintered wick and the heating plate can be increased.Also, the insertion portion of the sintered wick can be mechanicallyprocessed into a desired shape.

As described above, according to the evaporator for a loop heat pipesystem according to the present embodiment, since the contact areabetween the sintered wick and the heating plate is increased compared tothe conventional technology, the contact conductance is increased.

While this invention has been particularly shown and described withreference to exemplary embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. An evaporator for a loop heat pipe system comprising: an evaporatorsection having a sintered wick formed by sintering a metal powder, inwhich a working fluid permeating through a plurality of pores in thesintered wick is heated so that the phase of the working fluid ischanged to a vapor state; a condenser section in which the phase of theworking fluid transported from the evaporator section is changed from avapor state to a liquid state; a vapor transport line connecting betweenthe evaporator section and the condenser section to transport theworking fluid, whose phase is changed to a vapor state by the evaporatorsection, to the condenser section; and a liquid transport lineconnecting between the condenser section and the evaporator section totransport the working fluid, whose phase is changed to a liquid state bythe condenser section, to the evaporator section, wherein the evaporatorsection comprises: a heating plate formed of metal and receiving heatfrom a heat source; a sintered wick coupled to a surface of the heatingplate and receiving heat; a plurality of grooves formed in a surface ofthe heating plate contacting the sintered wick and functioning as apassage though which the working fluid whose phase is changed to a vaporstate by the sintered wick is exhausted through the vapor transportline, wherein the grooves are formed in a side surface of the heatingplate, each of the grooves having a bottom surface and two sidesurfaces, and the sintered wick is partially inserted in each of thegrooves so as to contact at least a part of the two side surfaces ofeach of the grooves.
 2. The evaporator of claim 1 wherein the part ofthe sintered wick inserted in each of the grooves is an insertionportion, both side surfaces of the insertion portion contact the twoside surfaces of each of the grooves, and a lower surface of theinsertion portion is any one of a downwardly bulging shape, an inwardlydepressed shape, and a flat shape.
 3. The evaporator of claim 2, whereinthe heating plate comprises a lower plate portion having a circular discshape and a wall portion extending from a circumferential portion of thelower plate portion, the sintered wick is coupled to an inner surfacehaving an upper surface of the lower plate portion and an inner surfaceof the wall portion of the heating plate, and a cover member is providedin an upper portion of the wall portion of the heating plate and theliquid transportation line is coupled to the cover member.